The present invention relates to a method of and a system for tightening threaded connectors, such as bolts, nuts, etc.
More particularly it relates to a method of and a system for tightening of threaded connectors with the use of a plurality of fluid operated torque tools. Methods of the above mentioned general type are known in the art. Such methods have to be further improved.
It should be understood that since the replacement of asbestos gaskets in industry, the gaskets which are used now are very sensitive. If one of the gaskets is squashed by mistake, the flange has to be disassembled again to replace the damaged gasket. This happens quite frequently in assembly or becomes visible as a result of a later leakage.
The problem with tightening flanges is that the tool flange faces are usually not parallel to one another. When torquing the bolts with one tool, the job has to be done in increments of 25, 50, 75 100% of the desired torque in a criss-cross manner, so as to bring down the flange faces and then to apply the load to the bolts via torque. This is extremely time-consuming.
When torquing with multiple tools, the bolts on the closed end become tighter while the bolts on the open end are still relatively loose. This causes crushing of the gasket and later leakage. When using hydraulic tensioners in multiples around the flange, each one applies the same identical loads to the bolts while stretching the bolts. This also means that the closed end of a flange obtains the same load as the open end of the flange initially. This could crush the gasket before the flange faces become parallel to each other. As the gap between the flange faces looks parallel even when it is not so, a way had to be found to automatically bring down the open end first without applying any force to the closed end.
Accordingly, it is an object of present invention to provide a method of and an apparatus for tightening threaded connectors, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of tightening threaded connectors which include the steps of using a plurality of fluid-operated torque tools each engaging with a respective of one threaded connectors; sensing when at least one of the fluid-operated torque tools reaches a point during an advance stroke when it permits a return ratcheting; and automatically retracting all pistons of all fluid-operated torque tools even if a rest of the pistons of the fluid operated torque tools is not advanced to a point when the return ratcheting of the tools is permitted.
It is another object of present invention to provide a system for tightening threaded connectors which includes a plurality of fluid-operated torque tools each engaging with a respective of one threaded connectors; sensing means operative for sensing when at least one of the fluid-operated torque tools reaches a point during an advance stroke when it permits a return ratcheting; and means for automatically retracting all pistons of all fluid-operated torque tools even if a rest of the pistons or the fluid operated torque tools is not advanced to a point when return ratcheting of the tools is permitted, comprising a plurality of fluid operated torque tools.
When the method is performed and the system is designed in accordance with the present invention, the flange faces are brought together so that they become and stay parallel to each other. The nut that is the loosest always turns so that all nuts are only turned simultaneously when the load applied to their bolts is close to equal. The looser nuts will always be brought up to the level of the tighter nuts, yet the tighter nuts will never keep the flange out of parallelism as all nuts are on hand-tight to begin with. In other words, even parallel flanges have a tendency to settle, thus becoming uneven again. With the present invention, the open end will at all times get the torque, while the close end has no torque applied until they become parallel, at which point all bolts are at equal load, all nuts get torqued and the flange faces are brought together with equal compression in circumference.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.